A typical method for mounting an electronic chip component, such as a ceramic capacitor, on a circuit board is to perform surface mounting with which terminal electrodes of an electronic component are directly soldered onto a land of a circuit board. However, this method can cause problems such as cracking of an electronic component or separation of terminal electrodes from the body of an electronic component due to causes such as a stress that occurs due to a difference in coefficient of thermal expansion between the circuit board and the electronic component or a stress that occurs due to a bend of the circuit board.
A method employed for addressing the above-described problems is to reduce the stress on an electronic component by bonding terminal strips, made of an elastic metal plate, to the terminal electrodes of the electronic component from both sides in such a manner that the strips are opposed to each other and by mounting the terminal strips on a circuit board.
Examples of a method for bonding the above-described terminal strips to the terminal electrodes include the followings: a method for soldering terminal strips to terminal electrodes (for example, Japanese Unexamined Patent Application Publication No. 2002-280274); a method for soldering terminal strips to terminal electrodes by preparing a lead frame to which a large number of terminal strips are coupled and causing an electronic component to pass through a reflow furnace in a state where the electronic component is held between the terminal strips (Japanese Unexamined Patent Application Publication No. 2008-205455); and a method for directly diffusion-bonding terminal electrodes and terminal strips to one another using heating and electric conduction while the terminal electrodes and the terminal strips are brought into contact with one another (Japanese Unexamined Patent Application Publication No. 2010-016326).
Japanese Unexamined Patent Application Publication No. 2002-280274 discloses a method of soldering terminal strips to terminal electrodes of an electronic component with molten solder while the terminal strips are being pressed against the terminal electrodes by a pair of pressing members. In this case, the terminal strips are soldered to the terminal electrodes while being pressed against the terminal electrodes and thus the bonding strength is excellent. In the case of, however, bonding terminal strips to a large number of electronic components, a heating furnace has to contain the electronic components against each of the terminal strips as the terminal strips are pressed by a pair of pressing members. Thus, equipment for continuously pressing and holding electronic components and terminal strips is required inside the heating furnace, leading to high costs and low productivity. This method also involves an increase in heat loss due to the need for large heat capacity to accommodate the pressing members.
Japanese Unexamined Patent Application Publication No. 2008-205455 discloses a method of soldering terminal strips to an electronic component by forming a large number of terminal strips that are coupled to a lead frame, holding the electronic component between the terminal strips with solder, and inserting the electronic component held between the terminal strips into a heating furnace. The lead frame is then cut off the terminal strips. This method does not involve pressing of individual electronic components using pressure members and thus enables a reduction of equipment costs compared to those in the case of Japanese Unexamined Patent Application Publication No. 2002-280274. This method, however, may not provide highly reliable soldering since the terminal strips are soldered to the electronic component while the electronic component is being held by only the spring elasticity of the lead frame and thus the terminal strips are not firmly pressed against and attached to the terminal electrodes. Moreover, the preparation of the lead frame including a large number of terminal strips has a high cost and the lead frame cut off after soldering is not reusable and thus wasteful.
Japanese Unexamined Patent Application Publication No. 2010-016326 discloses a method for diffusion-bonding terminal electrodes and terminal strips to one another without using solder. The method is free from the problems incidental to soldering. However, in order to achieve diffusion bonding having a desired bonding strength, the following conditions are required: a duration of conduction of 300 ms to 1000 ms; a welding pressure of 30 N to 50 N; and a maximum temperature at a joint portion within the range of approximately 700° C. to 900° C. (paragraph 0047). Performing pressing and attachment under such a high temperature and a high pressure highly damages the electronic component. If the electronic component is a ceramic electronic component, the electronic component can be subjected to a larger number of defects such as cracks. If metal in the terminal strips is sufficiently diffused into the terminal electrodes while the electronic component is prevented from being damaged, it takes a relatively long bonding time of 1 sec or more, thereby possibly leading to low productivity.
The present disclosure thus aims to provide a method for manufacturing a terminal-strip-equipped electronic component that can solve the above-described problems of various bonding methods and provide a terminal-strip-equipped electronic component.